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[time-freq] Rockwell MicroTracker GPS Module

Eric Lemmon wb6fly at verizon.net
Sun Aug 8 16:57:35 UTC 2010

Thanks to valuable assistance from James Miller and others, I have all three
of the Rockwell TU00-D200-401 modules I recently bought from Weirdstuff
working.  Well, sort of.

Even when connected to a roof-mounted commercial GPS timing antenna, the
modules take almost 20 minutes to lock up.  Once that happens, the module
starts outputting GGA and VTG sentences.  Curiously, although the
MicroTracker has five channels, it never locks on more than four- even when
my ThunderBolt receiver has seven or eight satellites in lock.  I'll admit
that getting a GPS module for less than ten bucks is no guarantee of
exceptional performance, but it seems odd that the MicroTracker performs so
poorly.  Another radio club member bought several of the same modules, and
has similar results.

I am posting this message to see if any readers can tell me what the Rakon
TCXO is used for, and what effect an adjustment of the oscillator's trimmer
will have.  It is very tempting to just mess with the screw and watch what
happens, but I learned long ago that a "diddle-stick artist" can easily turn
a working unit into a doorstop while trying to "improve" its operation!  I
have a well-equipped radio bench, so if I knew what result to look for while
adjusting the TCXO, or what test point to monitor, I would be ready to make
the leap.  The TCXO is marked "10.949297 MHz" and I could pick up a very
weak signal at that frequency with a sniffer probe.

I have created a two-page PDF information sheet regarding the capabilities
and connector pinouts of the TU00-D200-401 MicroTracker, and have submitted
same to the Weirdstuff folks for posting on their Web site.  The information
now on that site claims that the MicroTracker is a 12-channel module and has
the pinout of a Jupiter module.  In fact, it is a five-channel device and
has a different pinout.  I will be happy to send my info sheet to anyone who
requests it, just email me at mycall at verizon dot net.

73, Eric Lemmon WB6FLY

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